You’re ex-boyfriend is a total idiot. You don’t just decide one night to have anal sex for the first time and go at it without a lot of preparation.
It takes some slow introduction to learn how to totally relax the sphincter. It takes a ton of lube. You cannot be tense or fearful and enjoy anal sex.
It might take a number of sessions with fingers and sex toys before the anus is ready to accept full penetration.
It is a slow process for the first time and it should not be rushed. It needs to be done lovingly.
It should not be unbearably painful. And if at any time the receiver wants it to stop, well, no means no and consent can be withdrawn.
So please don’t label yourself forever as someone who doesn’t like anal sex and refuse to try again with someone who actually loves you and respects you enough not to hurt you. And choose someone who knows what the hell he is doing. This guy didn’t qualify on multiple counts. How you choose to label his brutally bad behavior and poor sexual technique is up to you.
You justifiably didn’t like anal sex with this dolt. An uneducated, unloving, controlling, selfish moron who had no idea how to properly go about it.